July 26, 2012 at 7:45 pm
Hey, can somebody give me some info on how good/bad performance is with MOLAP storage on fusion-io cards, running on windows 2008 x64 and sql 2008 x64 SSAS?
I have seen a lot of talk about sql tempdb performance gains and other general faster query times for relational engine, but cannot seem to find articles/experiences with OLAP query/processing results.
Since SSAS relies on storage engine for part of its computations, I would imagine storing/processing on SSD cards should result in fast access times?
July 30, 2012 at 9:12 am
It depends on the queries you run and data access patterns that result, so there is no one-size-fits-all answer. SSDs have much higher random-access read/write speeds than hard drives, but good storage arrays can deliver comparable sequential access speed. So if your queries result in significant portion of random-access to disk (say, at least 10-20%), then you'll see a decent performance boost. (Assuming that I/O is where your bottleneck is, not CPU or RAM.) And if the majority of I/O is random-access, then you can see some pretty spectacular results by introducing an SSD.
I work at VeloBit -- we do a lot of SSD performance measurements and publish them on our VeloBit Storage Performance Blog[/url]. You can find some specific Fusion-io performance numbers including the maximum throughput levels.
Another consideration for performance is whether you can actually fit all of the data onto the SSD. SSDs are mighty expensive and if you have a more than a few GB of data, you start to feel the pain, especially if your dataset grows. Fusion-io in particular is a high-end/expensive SSD.
If you can't fit all of the data onto the SSD within your budget (and most folks can't), then you have two options to consider. The first is tiering your data, which is painful to do and manage, especially as datasets change over time. The second option is to use the SSD as a cache so that you still get the high-performance SSD access but you don't have to pay for lots of SSDs and you can even use a lower-end SSD. (Here at VeloBit, we make software that does the latter, and we see users reducing their offline processing time by 95%!)
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